1. Field of the Invention
The present invention relates to an LSI for controlling the display of picture data such as letters or drawings and, more particularly, to a display system controller which is suitable for superposed display of a plurality of frames.
2. Description of the Prior Art
In accordance with a highly integrated memory LSI, the cost of a graphic display equipped with a high-capacity memory is dropped so that letter displays are processed by a full bit map. In accordance with the high detail of a display device, there is an increase the quantity of information to be handled. In these displays, the display control of letters and drawings is handled by a special purpose LSI (or a CRT controller).
Specifically, the CRT controller functions to sequentially output memory addresses from the display starting address which is preset in conformity with the raster scan. The CRT controller has another function to output a synchronizing signal for driving the display system. A CRT controller of the prior art type for displaying data from a plurality of independent frames, is shown in FIGS. 1 and 2.